Heating assembly for pipe line



P 14, 1955 F. c. BENNETT ETAL 3,206,179

HEATING ASSEMBLY FOR PIPE LINE Filed Nov. 15, 1963 COS/in g m och/n6 603 source INVENTORS. Foe/er 6. 66/7/3679 BY Frank E. Robb/n6 United States Patent 3,206,179 HEATING ASSEMBLY FOR PIPE LINE Foster C. Bennett and Frank E. Robbins, Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Filed Nov. 15, 1963, Ser. No. 324,021 5 Claims. (Cl. 263-4) This invention relates to means for transporting molten metal or molten inorganic salts through pipes or the like and particularly to an assembly for transporting molten non-ferrous metals from a source of molten metal to a utilization device which is spaced therefrom.

In die casting operations using non-ferrous metals such as magnesium, zinc or aluminum, for example, a reservoir of molten metal is maintained at a supply pot and is fed from there to casting machines to maintain in the casting machine a predetermined (but smaller) inventory of molten metal.

A pipe line connecting the supply pot and the casting machine (or machines) is the means through which the metal is transported to the casting machine. The pipe line must, of course, be heated to keep the metal in it in a molten condition.

Keeping the pipe line heated and the metal within it molten is a more complicated task than appears at first glance. Vertically disposed pipe lines are particularly hard to heat with gas flames.

Such pipe lines are easily affected by air drafts which often occur in the buildings where casting operations are carried out. Freeze ups in the line are not uncommon Where drafts impinge on metal carrying pipe lines.

Even when air drafts are not present to an excessive degree, where one side of the wall surface of the pipe line is heated directly by gas flames, the heat emission from the other (unheated) side is often so great that cold spots in the line occur which at unexpected moments plug the lines.

When enough heat is applied to such a line to insure that flow will be maintained, excessive oxidation of the line occurs and the expected life of the pipe line will average about 30 days. Repairs are expensive. Leaks of molten metal are very hazardous. Heating costs are high, too, because of the large amount of gas consumed where exposed pipe lines are used.

Attempts have been made in the past to remedy the situation by surrounding the pipe line and burner with an insulating shroud, but this has not been really satisfactory because the shroud is bulky and often cannot be fitted onto the line because of space restrictions. Further, when the pipe must be replaced the shroud is usually damaged to a substantial degree, requiring additional down time of the machine while the shroud is repaired or rebuilt.

Attempts have also been made to wrap insulation around the line, leaving holes in the insulation at points where the heater flames are to impinge. This method is at a disadvantage during operation because the insulation between the points of impingement of the flame prevents, at least to a degree, the spreading of the heat from the flames along the pipe line. Non-uniform heating results. Consequently, excessive heat is required from the flames (usually requiring special mixtures of gas) in order to maintain a minimum line temperature which is above the melting point of the metal which the line is to transport.

When uneven heating occurs the pipe may bend or distort so that the holes in the insulation no longer are aligned with the heating flames. Such binding and distortion of the pipe line is common, however, even when an uncovered pipe line is heated.

Also, when a pipe must be replaced the insulation is ice lost to a substantial degree, too, because the embrittled, compacted insulation often cannot successfully be removed and replaced.

While the problems attendant to heating lines which transport molten metal are well exemplified by the discussion of specific problems in the metals casting industry, similar problems exist where molten inorganic salts, for example, are transported through pipe lines or the like.

Accordingly, a principal object of this invention is to provide an improved assembly for heating lines which are used to transport molten non-ferrous metals or inorganic salts.

Another object of this invention is to provide an improved, compact assembly for heating lines which are used to transport molten non-ferrous metal and in which the insulation is replaceable and reusable.

A further object of this invention is to provide an improved, more compact, easily replaceable insulation assembly for coupling to a heated line transporting molten materials.

In accordance with this invention a pipe line which is heated by heating elements spaced along its length has sections of insulation which are housed in a metal housing clamped over more than half the circumference of the pipe. The housing comprises discrete members which are disposed in end-to-end relationship along the length of the pipe line. The housing has centralizing elements disposed along its length to prevent the pipe from excessively compressing the insulation.

The insulated sections are easy to apply and take off the pipe line, reduce the heat input required to maintain the pipe line contents in a molten condition, and result in a longer useful life for the pipe line.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawing, in which FIG. 1 is a diagrammatical view of a heating assembly in accordance with this invention;

FIG. 2 is a plan view of an insulated section in accordance with this invention, and

FIG. 3 is a sectional view taken along the line 33 of FIG. 2.

Referring to the drawing, and particularly to FIG. 1, there is shown, in block diagrammatical form, a melting pot 10 for molten non-ferrous metal, such as magnesium, zinc, or aluminum, for example, and a casting machine 12 which delivers measured amounts of molten metal to a die, for example. A hollow pipe line 14 is coupled between the melting pot 10 and the casting machine.

eneat-h or beside the pipe line 14 and disposed parallel thereto is a gas line 16 whose length is substantially coextensive with the length of the pipe line 14. The gas line 16 has a plurality of burners 18 disposed along its length, the burners facing towards the pipe line 14 and spaced so that the flames 20 from each of the burners impinges directly on the pipe line 14. The spacing between each burner along the line 16 is about 3 inches on center, and the burners are disposed in a line and generally'perpendicularly with respect to the line 16.

A gas source 22 is coupled to the gas line 16 through the line 24 and valve 26.

A plurality of insulated members, indicated generally by the numeral 28, are secured to the line 14 by snap action coupling means.

Referring now to FIGS. 2 and 3, as well as to FIG. 1,

i it may be seen that the insulated members 28 each com- The housing 39 is composed of three elongated shapes or sections. The sections 34, 36 each are composed of elongated sections bent in an arc of approximately 120 degrees as measured transversely of the section, the longitudinally extending edges of each section being bent to form flanges 38, 48 and 40, 42, respectively. The flanges 38, 42 extend outwardly with respect to the convex surface of the section and the flanges 40, 44 extend inwardly with respect to the concave surfaces 50, 52 of the sections 34, 36.

The flanges 40, 44 extend inwardly at an angle of approximately 90 degrees for a distance of about inch.

The flanges 38, 42 extend outwardly for a distance of about A inch at an angle of about 90 degrees with respect to the adjacent part of the section of which they are a part.

A flat elongated section 46, usually coextensive in length with the sections 34, 36, is placed between the adjoining flanges 38, 42 as the sections 34, 36 are assembled to form a single continuous member which has an arcuate transverse cross-sectional configuration.

As assembled for use, the flanges 38, 42 are disposed adjacent to each other with the section 46 sandwiched between. The lower edge 60 of the section 46 extends .outwardly from the inner surface 50, 52 of the sections 34, 36 by a distance at least approximately equal to the width of the flanges 40, 44 (as measured transversely to the longitudinal axis of the section 28). Flanges 38, 42 and the flat section 46 are spot welded together, as at 58, for example.

Strips 54, 56 of fibrous insulating material, such as fibrous aluminum oxide and silica, for example, are disposed adjacent to the surfaces 50, 52. The edges of each strip 54, 56 bear against the flat section 46, flange 40, and section 46 and flange 44, respectively. The strips of insulation 54, 56, usually have enough body that they will, without the use of adhesives, remain in position adjacent to the surfaces 50, 52 during use. However, those skilled in the art will know how to retain the insulation in position by mechanical means should the insulation 54, 56 tend to separate from the surfaces 50, 52.

In operation, the insulated members 28, which have a relatively thin wall (22 gauge) made of stainless steel, snap over the pipe on the side of the pipe which is most remote from the point of impingement of the flames 20 emanating from the burners 18.

The snap action is achieved as a result of the springiness of the relatively thin wall thickness of the sections 34, 36, and the fact that the member 28 extends around more than half of the periphery of the pipe to which it is secured.

Because the edge 60 of the section 46 extends inwardly from the concave surface of the sections 34, 36 and contacts the pipe 14, the members 28 are held in position with the sections 34, 36 at least approximately equally spaced from the outer surface of the pipe line 14. The three line contact with the pipe 14 also tends to hold the members 28 in position .on the pipe 14 with no radial sliding despite the vibration to which such pipes are often subjected.

Further, the members 28 may be attached to pipes 14 which are in non-horizontal positions without slipping of the member 28.

It has been found that the insulation 54, 56, which may either be one thick layer as illustrated, or may be a plurality of layers, remains in place during use and is not compressed .or subjected to physical destruction during use or when the members 28 are installed on or removed from the pipe line 14.

'In one test insulation where the pipe line 14 was maintained at 1200" F. on its exposed surface, the temperature on the outer surface of the member 28 on the side remote from the flames 20 was 500 F. Thus, it may be seen that the member 28 in combination With the pipe 14 and heating apparatus, forms an effective,

simple means whereby molten metal may be transported from one reservoir to another or from a reservoir or casing machine to another utilization device.

While the invention has thus far been described in connection with pipe lines which are used to transport molten light metals from a melting pot to a casting machine, the pipe line or hollow conduit may be the heated delivery nozzle of a casting machine or it may be a pipe line through which molten inorganic salts are transported.

The insulating material may be anything which has suitable thermal insulating qualities and Will withstand the heat to which the members 28 are subjected during usage. One such material which has been used with success is fibers of aluminum oxide and silica which are supplied in the form .of a felt-like sheet.

The members 28 have been constructed for and successfully used on pipe 14 having outer diameter of from one to two inches.

A convenient length of the sections 28 has been found to be about twelve inches, although greater or lesser lengths may be used as required in individual installations.

When heating assemblies in accordance with this invention are used, the pipes 14 have substantially longer life (two to three times longer, tests show), heating costs are reduced, and changing of pipes 14, when they need replacement, is accomplished with little effort because the members 28 are so easily removed and then replaced on the newly installed pipes.

What is claimed is:

1. A pipe line heating assembly comprising (a) an elongated hollow metal conduit adapted to contain a liquid and having an outer wall surface which has a substantially circular configuration when viewed in transverse cross section;

(b) an array of gas heating elements, said elements being disposed in a single line along and spaced substantially uniformly from said conduit whereby flames from said heating elements impinge along the length of said conduit, and

(c) a plurality of elongated thermally insulated members having an outer metal housing which is arcuate in transverse cross section and is between and 270 degrees in extent, an inner surface adapted to face said conduit, and quick detachable means there- ,on adapted to be coupled to said conduit for attaching said members to said conduit, said housing having thermally insulating material disposed adjacent to the surface of said housing which faces said pipe line, said insulated members being coupled to said hollow metal conduit on the side of said conduit which is most remote from said heating elements.

2. A pipe line heating assembly according to claim 1, wherein said quick detachable means for attaching said insulated members to said pipe line comprises flanges which extend inwardly from said outer metal housing.

3. A pipe line assembly in accordance with claim 2, wherein spacer means comprising a metal plate which is secured to said metal housing extends inwardly from the surface of said housing which faces said pipe line, said plate being disposed approximately half way between said inwardly extending flanges.

4. A thermally insulated member for attachment to a hollow conduit whichis adapted to contain a liquid, comprising an elongated thin walled metal section of generally arcuate transverse cross-sectional configuration which exceeds 180 degrees but is less than 180 degrees in extent, and including axially extending edges and concave and convex surfaces, said metal section having flanges on its axially extending edges which extend inwardly with respect to its concave surface, at least one layer of thermally insulating material, said insulating material being disposed adjacent to said concave surface, and spacer means extending inwardly from said concave surface for maintaining a predetermined space 5 6 between said concave surface and any conduit to which 1,616,525 2/27 Booze 26348 the member is attached. 1,897,165 2/ 33 Endacott et a1. 137-375 X 5. A member in accordance with claim 4, wherein said 2,044,763 6/36 Bouton et a1 263-5 X spacer means comprises an axially extending metal strip. 2,618,293 11/52 Moran 2634 X References Cited by the Examiner 5 2,928,411 3/60 Johnson 137-375 X UNITED STATES PATENTS CHARLES SUKALO, Primary Examiner. 1,260,624 3/18 Bardeen 2635 JOHN J. CAMBY, Examiner,

1,316,190 9/19 Sackerman 2635 X UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,206,179 September 14, 1965 Foster C. Bennett et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 66, for "180", second occurrence, read 270 Signed and sealed this 16th day of August 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

4. A THERMALLY INSULATED MEMBER FOR ATTACHMENT TO A HOLLOW CONDUIT WHICH IS ADAPTED TO CONTAIN A LIQUID, COMPRISING AN ELONGATED THIN WALLED METAL SECTION OF GENERALLY ARCUATE TRANSVERSE CROSS-SECTIONAL CONFIGURATION WHICH EXCEEDS 180 DEGREES BUT IS LESS THAN 180 DEGREES IN EXTENT, AND INCLUDING AXIALLY EXTENDING EDGES AND CONCAVE AND CONVEX SURFACES, SAID METAL SECTION HAVING FLANGES ON ITS AXIALLY EXTENDING EDGES WHICH EXTEND INWARDLY WITH RESPECT TO ITS CONCAVE SURFACE, AT LEAST 